Conventional coaxial cable has a center conductor, a dielectric insulator with a single aluminum foil cover, one layer of braided shield surrounding the foil covered dielectric insulator, and a plastic insulating jacket covering the braided shield. Additionally, “tri-shield” and “quad-shield” versions of conventional coaxial cable are being increasingly used due their improved performance.
Tri-shield cable has a second layer of foil which covers the braided shield, while quad-shield cable has both a second layer of foil and a second layer of braided shield over the second layer of foil. As a result of the additional shielding layers, tri-shield and quad-shield cables have overall thicknesses or diameters greater than that of common (i.e., dual-shield) coaxial cable.
An example of conventional quad-shield cable is shown in FIG. 1. As illustrated, the quad-shield cable 100 includes a center conductor 102, a dielectric insulator 104, an inner aluminum foil cover 106, an inner layer of braided shield 108 surrounding the inner foil cover 106, an outer aluminum foil cover 110, and outer layer of braided shield 112 surrounding the outer foil cover 110, and a plastic insulating jacket 114 covering the outer layer of braided shield 112.
The additional shielding layers provide extra insulation between signals internal on the coax and over the air signals, thus allowing the cable to provide a stronger signal over a longer run, which can be important for high definition (HD) and ultra-high definition (UHD), or 4K, television. The foil covers 106, 110 provide high frequency shielding, while the layers of braided shield 108, 112 provide low frequency shielding and add strength to the cable. Regarding the low frequency shielding of the layers of braided shield 108, 112, the shielding effect of two layers of braided shield having lesser coverage may surpass the effect of a single layer of braided shield having greater coverage. For example, two layers of braided shield having 60% and 40% coverage, respectively, may provide a greater shielding effect than a single layer of braided shield having 100% coverage.
As a result of the additional layer of foil or the additional layers of foil and braided shield, tri-shield and quad-shield cable are thicker than common coaxial cable. In the case of quad-shield coaxial cable, the additional layers of foil and braided shield make it more difficult to prepare the cable for connector installation. It can also be difficult to install the connector on the quad-shield coaxial cable due to the thickness added by the additional layers. Also, since the inner foil cover 106 is sandwiched between the two layers of braided shield 108, 112, both sides of the inner foil cover 106 can be abraded during installation and/or use, thereby causing the shielding to break down.